1. Field of the Invention
The present invention relates to an array splice for ribbon-like multi-core optical fibers and particularly to an array splice for multi-core optical fibers with the use of an ultraviolet-curing adhesive agent taken into consideration.
2. Description of the Prior Art
Splices for optical fibers having such features as low loss, long distance transmission, large-capacity transmission, no electromagnetic induction, small diameter, and explosion-proof property are used in large-capacity basic trunk lines for long distance including submarine cables, local inter-office trunk lines, inter-office and subscriber's transmission systems, power systems for communications only, monitor control circuits for railways and superhighways, and computer networks.
An optical fiber 4, as shown in FIG. 6, has a construction in which a glass core 1 having a diameter of about 10 .mu.m or about 50 .mu.m and a glass clad 2 having an outer diameter of about 125 .mu.m and concentrically surrounding said core are covered with a silica glass jacket member 3 having an outer diameter of about 250 .mu.m or about 900 .mu.m, the refractive index of the core 1 being somewhat higher than that of the clad 2 so as to provide a total reflection type optical path which prevents light from leaking through the core. This optical fiber is in the form of either a single-core type optical fiber consisting of a single optical fiber or a multi-core type optical fibers consisting of a plurality of optical fibers gathered together in ribbon form.
In connecting optical fibers 4 together, the axes of the cores are aligned with each other to minimize connection loss and in this condition the optical fibers are positioned and fixed on a splice and use is made of such bonding medium as an ultraviolet-curing adhesive agent. In the case where the optical fiber 4 is in the form of a ribbon-like multi-core optical fibers, a base 6 having a plurality of parallel V-shaped grooves 5 is used as a splice (see FIG. 7).
In the case where the aforesaid base 6 having V-shaped grooves 5 is used, in order to decrease connection loss it is necessary that the optical fibers 4 be positioned and fixed on the base 6 so that the clads 2 of the optical fibers 4 having their jacket members 3 stripped are closely contacted with the bottoms of said V-shaped grooves 5. However, to correctly position and fix the individual optical fibers 4 in the V-shaped grooves 5, it is necessary to adjust the relative position of engagement between the individual optical fibers 4 and the V-shaped grooves 5 to ensure a uniform push-in pressure over the entire length of the optical fibers 4. However, since the optical fibers 4 have a small diameter, the positioning and fixing often tend to be unstable and the butted front ends of the optical fibers often tend to escape from the bottoms of the V-shaped grooves 5 to a space on the opposite side; thus, minimization of connection loss of optical fibers has been greatly limited.
For the purpose of solving the aforesaid problem, the applicant of the present invention previously proposed, in Japanese Patent Application No. 188663/1988, the use of a glass capillary tube 8 with an adhesive agent discharging groove 7 formed in the lengthwise middle portion thereof as a positioning and fixing jig or connecting member for optical fibers (see FIGS. 8 and 9). The use of this capillary tube type splice makes it possible to secure the positioning and fixing conditions which substantially prevent occurrence of connection loss between two optical fibers 4. In the case where optical fibers are in the form of multi-core optical fibers 10 each comprising a plurality of optical fibers joined together in ribbon form as shown in FIG. 10, however, smooth insertion of the optical fibers 4 has been very difficult since the diameter of the optical fiber insertion ports of the glass capillary tubes is small.